Altimeter



Janf 8, 1935. F. H. BRAKE 1,987,588

ALTIIMETER Filed Jan. 3Q, 1930 2 Sheets-SheeI l Jn. 8, F .HU DRAKEALTIMETER Filed Jan. 30. 1930 2 Sheets-Sheet 2 la' Passif/'a7 oooo oooo\Y" ooo@ E ooao ooo@ y #rei-need im. 8, i935 PATiazNT OFFICE ALTIMETERlflfgierlck H. linke, Boonton, N. J., assis-nor, by

mesne' assignments, to Radio Corporation of America, New York, N. Y., acorporation of Delaware Application January so, 19st, serial No.424,661.

isciaim..

v invention relates 'te electrical apparatus' i'orthe measurement ofdistances, and more .particularly to apparatus for determining -thedistance between a source of electrical wave en-,- I

'5 ers? anda riiecting surface. In my copending application-gema.247.190, tiled dan. 16. 1928, I have described the method ,of andapparatus for determining distances by l electrical energy of dennitewave length lo troni a source, and determining the distancebetwen'thesource and rene-ting surface by the redctionupo'n the source ci waveenergy re. `turned thereto by reilectionfijom the reflecting 15gg', Thepresent invention Aapparatus oi A. g the same general character, andanobject of the I :invention is to provide apparatus including rejlays foractuating sisnals when the Vdistance between the source and reilectingsurface reaches "iennitef and predetermined values. other iii-` i'ectsare to provide improved electrical and mearrangements of the elements ofthe 'j app'aratus which will facilitate the construction fof compactdevices that may be conveniently 25 installed inaeroplanes or the likewhere space and weight requirements are particularly rigid. .A furtherlobject is to provide apparatus of the type stated including a generatingunit and an `indicating unit that maybe located in any con- 30 venientpositions and operatively connected by a multistrand cable. These andother objects of the invention will .-4 be apparent from lthe followingspeciilcation when taken with the accompanying drawings 35 m Fig, 1 isadlagrammatic view of the electrical circuits of one .embodiment of theinvention, I

Fig, 2 is a view oi' another embodiment of the invention, the generatingunit being shown in :40 front'- elevation, and the indicating unit beingslivwn diagrammatically. ,Fig'. 3 is a front elevation of the indicatingunit 1.4 is a iront elevation of the indicating unit 45 shown'in Fig. 2,

. is a Perspective view, on an enlarged of one ot :the,circuit-controlling'elements oitiie indicating unit shown in Fig.' 2,and

lfig'n is an" explanatory diagram illustrating 5b nie operation of theindicating'uni't or rigs. 2

. Inhe drawings. the reference numeral 1 identitles the shielded housingof the generating unit f which includes the vacuum tube 2 having coupled'grid and .plate inductancesL, Li, respectively.

wieso-n f 'I'he cathode circuit of the tube is grounded upon the housing1 by a condenser 3 and, when the cathode is of the filamentary type, oneterminal of the cathode is conductively connected to the `housing by alead 4. The iilter mesh 5 in the 5 plate circuit completes theoscillatory circuits of the vacuum tube independent of the platebattery. The inductance L of the grid' circuit may be shunted' by a nxedcapacity C and by a condenser Ci that may be adjusted for tuning theoscillator to different wave lengths. The inductance Lz is coupled tothe grid inductance L and has terminals 6 to which the antenna,notshown. may be connected. I y

The generating unit also includes na relay of the double contact type,the current through the winding 7 determining the position'or thecontact arm 8 that is movable between the nxed contacts 9, 10. Amilliatnmeter 11 in the plate circuit oi the oscillator may be, andpreferably 2o is, carried by the generating unit.

The circuits of the generating unit will best be understood by ilrstconsidering the indicating unit which comprises a. casing 12 whichcarries signal devices such as lamps, 13, 14, respectively, and currentmeasuring instruments-15, 16; respectively. The indicating unit alsoincludes a pair of switches 17,' 18, respectively, an adjustableresistance 19 and preferably a current-limiting resistance 20. All ofthe circuitsot the generat- 3o ing and indicating units may be energizedfrom the cathode battery A and the plate or high tension battery B bymeans of a multistrand cable which includes leads connected to theterminals of the respective batteries and a plurality of leads forcompleting the electrical circuits between eiements of the generatingunit and elements'of the indicating unit.

The cable is of course of such length that the respective units may beVlocated in any desired i0y or convenient positions, and the cableterminates in plug connectors i'or cooperation with socket terminals -onthe units. .As shown in Fig. 1, the socket on the generating unit haseight tenninais while the socket on the indicating unit has t but seventerminals and the main cable extending between the two units comprisesseven strands indicated by the letters b to h, inclusive; The strand aof the cable does not extend be-y tween the two units but connects thehigh poten- -tiai side-of the plate battery B to the generating unitterminal of the plate circuit. Strand b' of the battery section. of thecable is connected to strand b that extends to the junction ot oneterminal of, the instrument 16 andthe resistance 19 55 ot the indicatingunit. Strands c and d extend between relay contacts 9,- and the signallamps 18, 14, respectively, theasecond terminal of each lamp filamentbeing grounded on the casing 12. One terminal of relay winding 7 isgrounded on the casing l and the strand e of the cable connects thesecond terminal of the relay winding 7 to a terminal of the instrument15, this circuit continuing through the second instrument 16 to thestrand b. The strand l of the battery section is connected to strand fof the connecting cable which leads tothe contact arm of switch 17 otthe indicating unit but which is not connected to any element of thegenerator unit. The strand a connects the-xed contact of switch 17 tothe cathode ofthe vacuum tube 2 through the resistance 2l that ismountedin the generating unit. 'I'he strand h. of the battery cable connectswith the strand h that is grounded upon the generating unithousing 1 andthe indicating unit casing l2.

'Ihe contact arm 8 of the relay is connected to the highpotential leadof the cathode battery completed through battery strand a. b', b. switch1s, strana @and lead 4. when switch isis closed, thejindicating systemis shunted and the oscillatoru'nfay be adjusted for best operation inthe usual-manner.

when the shunt switch 18 is opened. the relay 'z and the instruments 15and 1e are connected unshunted between the low potential side of theplate battery and the grounded filament terminal of the tube. When thecontact arm 8 engages contact 9 or 10, it completes a circuit forenergizing the lamp 13 or 14, respectively, from the cathode battery A.

Assuming the apparatus to be mounted upon an aeroplane and radiatingelectrical wave energy from the antenna connected to terminals 8, theoperation is as follows. As the plane approaches the ground,thereflection back to the oscillator of a. portion of the energyradiated therefrom will produce reactions that are characterized byalternate maxima and minima of oscillatory current ow when the planereaches levels spaced from the ground surfaces by multiples ofone-quarter the length of the radiating wave. When the plane is at suchelevation that the effects of this reected wave energy are substantiallyzero, the resistance 19 is so adjusted by dial 19', Fig. 3, that thenormal plate current in relay winding 7 and instruments 15, 16 is justneutralized by current flowing from the cathode battery A through thecurrent-limiting resistance and the adjustable resistance 19. Thisternately rises to a maximum and falls to a minimum. Since the normalplate current was neutralized, these changes in plate current areindicated by the instruments 15, 16 and the contact arm 8 of the relaymoves alternately towards the contacts 9 and 10. The sensitivity of therelay may be so adjusted that the signal circuits will be closed only attwo chosen levels above the ground. The passing-of other maxima andminima levels may be noted from observation of the instruments but thepassing of the last tv'vosig-l nificant levels will be indicated by thelighting of the signal lamp 13 and the signal lamp 14.

I have discovered that when the signals take the form of signal lamps,the heavy rush of current at the instant that the relay contacts areclosed will cause the contacts to stick. The current-limiting device 22is so chosen that the initial surge of current, before the lamp lamentsare heated, is held to a value which will not" cause sticking. A chokecoil may be used for this purpose but a resistance is usually equallyeiective and more convenient. lamps having a cold resistance of some 6or 7 ohms and a hot resistance of about 30 ohms, I have found that thecurrent-limiting device 22 may take the form of an ordinary wireresistance of 15 ohms to prevent sticking contacts in a'commercialhigh-sensitivity relay.

The apparatus shown inFig. 2 differs from that illustrateddiagrammatically in Fig. 1 only as to the construction of the indicatingunit. Only the front panel of the generating unit is shown at the leftside of Fig. 2, but it is to be understood that the circuit arrangementis or may be substantially the same as that shown diagrammatically inFig. 1. The switches 17, 18 and the resistances 19, 20, in thisembodiment may be identical with those previously described and theirconnections to the cable and to the elements of the generating unit arealso identical with those previously described. In this form, theseparate miliiammeters 15 and 16 are replaced by a single instrument-15' that indicates the direction as well as the magnitude of currentflow. In this embodiment, however,

the secondary 'circuits of the relay do not include the signal lamps butinclude elements for controlling the signal system. The strands c and dof the cable extend between the relay contacts and the solenoids 23, 24,respectively, that have as their common armature the arm 25 of the leverof -a Geneva escapement. As the current ow in the relay winding 7 passesthrough successive maxima and minima, the escapement lever will berocked back and forth to permit the step-by-step movement of a rotaryswitch.

For the particular signal system shown in Figs. 2 and 4, the rotaryswitch will operate on a cycle of six steps. Attention is directed tothe fact that the cylindrical surface of the switch drum that is shownin the diagrammatic view, Fig. 2, represents what may be considered adevelopment of that portion of the cylindrical surface which correspondsto the six steps of one cycle. One terminal of each of a series ofsignal lamps 28 is connected to the xed contact of switch 17 andtherefore to the high potential side of cathode battery A when theswitch is closed. The other terminals of the respective lamps 26 areconnected to individual brushes or contacts 27 that engage the surfaceof the cylindrical switch drum For example, with 28. I n the firstposition of the rotary switch, nonev of the contacts 27 "engages theconductive-seg- Vvalue or values corresponding to the lighting of someof the series of lamps, means is provided for decreasing the sensitivityof the relay. As previously described,'the closing of the switch 18 willshunt the indicatingcircuits, and the system for automaticallydecreasing the sensitivity of the relay preferably comprises a series ofresistive shuntJ circuits that are veffectively in parallel with theshunt switch 18. As shown in Fig. 2, one terminal ofthe plurality ofresistances 31`, 32, is

connected to the movable arm oi'swith -18 and the other trininalsof theresistance are c on- -nected to individual contacts 33 that are sopositioned with reference tothe contour of the con'- tacting segment 29of the switchdrum that the resistivev shunt circuits are progressivelyclosed met the msc lamp is energized.

Simultaneously with the shunting of the relay -winding 7 by theresistances 31 or 32, it is essential that a second resistance beincluded in series with the shunted vwinding 7 to maintain theeilectiveseries resistance of the relay constant.` If this is not done, the fzeroadjustment of the relays, as established by the current introduced frombattery A through resistance 19, will be disturbed.

Between the second terminal of the instrument 15'Iand the connectingstrand e, there are introduced two series resistances 34, 35 and leads36, 37, 38 extend from `the terminals of these resistances to contactsthat engage the split ring 39 on the rotating switch drum 28. As' shownin the detail view, Fig. 5, the ring 39 has one gap 40 that, in certainvpositions of the drum, lies .between the contacts associated withadjacent leads 36, 37 or 37, 38, and-a second gap 40'which is sopositioned that it lies under and is spanned by the respective contactsin three diiferent adjustments of the drum.

As shown in Fig. 2, the gap 40 is in such position with reference to thethree contacts that it will break the shunt circuit around theresistance 34 when the drum has advanced two steps; This position of thedrum therefore shunts resistance 31 across the relay winding 'I andincludes the resistanoe 34 Ain series with the shunted winding.

The, series of lamps 26Y are preferably arranged4 in a vertical columnon the panel of the casing 12 and adjacent a scale Vor indicator card 41that carries notations, opposite the respective lamps, of the elevationat which they severallamps will be lighted. y'I'he contact cylinder ordrum 28 `is rotated by a coil spring 42, the winding key 43 for thespring preferably extending through the front panel of the casing 12'. Y

'I'he operation of this form of indicating unit will be described inconnection with the diagram constituting Fig. 6. In this diagram, theseries of linesI to IV, inclusive, indicate levels separated from eachother and from the ground line G by one-quarter wave length. y When theplane is at such elevation that the effects of reilected wave energy aresubstantially zero, the adjustableresistance 19 is set, by dial 19" tobring the pointer of instrument 15' "tozero, and, if ne'c ry, the

Vapparatus is re-set to extinguish all lamps. As the plane reaches theelevation of the plane I, the current flow through the relay closes oneset of contacts to energize the solenoid 24, Fig. 2, and the spring 42turns the switch drum 28 to close the circuit through the first light.As the plane continues along the descending portion of its path,indicated by the solid line D, the current corresponding to the peakvalue at the second significant level, line 1I, closes the other set ofrelay contacts and the escapement permits the spring 42 to move thevdrum forward one step t'o close the circuit through the second` lamp 26.At the same time, the contact associated with the resistance 31isengaged by the segment 29 of the drum switch. When this resistiveshunt circuit is closed, the plate current passes through the seriesresistance 34 and then divides and only a portion flows through thewinding 'l of the relay, the sensitivity ofthe relay being reduced tosuch extent that .the recurrence of the current peak corresponding to'the level at line I will not close'the contacts. If

the altitude should increase after the plane has fallen below the levelof line II, the repetition of the closing of the relay contacts thateected the previous release ofthe escapement can not give a falseindication since the escapement lever must swing in the oppositedirection to permit a further rotation of the drum. Due to the resistiveshunt 31, the relay can not close the contacts when the soV plane risesabove or again drops through the level of line I. As indicated by theseries of light line and heavyline circles in Fig. 6, the upper lampswill light when the plane passes through the tlrst signiilcant levelland the second lamp will light as the plane passes the second level,but the sub-4 sequent passage through one or both of these levels willnot result in the lighting of additionai lamps.

The repeated passing cf a significant level will be indicated oninstrument 15 by repeated readings corresponding to the current peak forthat level, and a continued zero reading of the instrument usuallyindicates that the plane has risen above the altitude at which theeffects of reilected energy disappear.

The current peak corresponding to level III is in the same sense as thecurrent peak for level I but is of substantially greater magnitude.Although the relay was rendered less sensitive by theresistive shunt 3l,the currentow corresponding to level III is suiiicient to again closethe relay contacts that energize the solenoid 24 and the cylinder istherefore rotated an additional step to close the third lamp of theseries. This movement of the switch closes the second resistive shunt 32and inserts the series resistance 35, but the current peak for level IVis of such magnitude that the, second set of relay contacts ls closed asthe plane passes through that level. The lighting of the complete seriesof lamps indicates to the vpilot that he has fallen through a certainrange of altitude and is within a definite selected distance of theearths surface. For resetting the altimeter when tlight is resumed,cr'to reset the altimeter after one or more lamp circuits have beenclosed and the plane takes an ascending path such as indicated by thebroken line E, the operator adjusts the value of the resistance 19 toestablish current peaks similar to those produced by reflected waveenergy. Assuming that the plane followed line E after two of the lampswere lighted, the sequence of lamp operation incident to the resettingof the aitimeter is indicated diarammatically by the several columns ofcircles/ which are grouped within the bracket F. By appropriatemanipulation of the adjusting dial 19' of the resistance 19, theoperator may simulate the occurrence of the current peaks whichcorrespond to the levels III and IV. As the dial of resistance 19 ismanually operated in this manner. the first step will light the thirdlamp of the series and the second step will light the fourth lamp, thusreproducing the condition corresponding yrto the landing of the plane.Upon adjusting resistance 19 to effect-the next step in the cycle, thecircuit through the upper lamps is broken and only the two lower lampsremain lighted. Adjusting the resistance 19 in the opposite sense eectsthe nal step in the cycle and all of the lamps are extinguished. Ihevalue of resistance 19 is then so adjusted that the pointer ofinstrument is at zero, thus resetting the apparatus for.

further use.

While I' have shown a series of four lamps, it will be understood that agreater or less number may be employed and that the fth or resettingstep will not be necessary if an odd number of lamps are employed. Foruse as an altimeter on an aeroplane or the like, the signal devices dopreferably take the form of lamps, but it will be apparent that othersignals suchas buzzers, bells or the .like may be energized by therelay. When the apparatus is employed on the ground for detecting thepresence of an aeroplane above the oscillator, the relay and switch maysuccessively close signaLlight circuits and flood light circuits at thelanding field.

The physical arrangement of the generating unit, the indicating unit andthe parts thereof may of course be varied within wide limits to adaptthe distance measuring apparatus for any particular or desired use. Foruse yon aeroplanes,

` the two units and connecting cable are particularly advantageous,since only the indicating unit need be mounted near the operator, butwhere economy of space is not important, all of the parts may becontained within e/single cabinet.

While I have illustrated the generator of electrical wave energy as asimple oscillator employing but one tube, it will be apparent that theoscillator may take the form of a master oscillator and an amplifiertube or tubes. In such an ar- .5'0 frangement, the relay winding will beincluded in a circuit of one of the amplifier tubes that constitutes apart of the complete vacuum tube/ generator.

It" will-be apparent that the invention is not limited to the particularembodiments which are herein illustrated and described, since the aboveand other changes inthe several parts, their relative construction andarrangement may be made without departing from the spirit of myinvention as set forth in the following claims.

-l. In an altimeter of the reflected wave energy type, the combinationwith a source of electrical waves, a radiator for radiating wave energyinto space, and a relay having the solenoid thereof in a circuit of saidsource in which alternately occurring maxima and minima reaction effectsare produced by venergy returned to the source from a 4predeterminedvalues, of a plurality of signal device`s-,-a.nd means includingcircuits controlled by gizing said devices to produce at least threedifferent signals corresponding respectively to three differentdistances between said source and surface.

.2. In distance measuring apparatus of the reected wave energy type, thecombination with a vacuum tube oscillator which may be connected toradiating means, sources of current for energizing said tube, and arelay having its solenoid included in a circuit which forms a path forthe space current of said oscillator tube, of indicating apparatuscomprising currentmeasuring means in a space current path of saidoscillator for indicating the alternately occurring maxima and minimaeffects produced by that portion of radiated wave energy which isreflected back to said oscillator as the distance between the source anda reflecting surface is progressively decreased, signal devices in thesecondary circuit of said relay. and means for adjusting the relay sothat the signal devices arel alternately energized when the distancebetween said oscff lator and a reecting surface reaches predeterminedvalues corresponding to maxima and to minima effects of reflected waveenergy.

3. The invention as set forth in claim 2, whereinsaid current measuringmeans includes two ammeters oppositely connected in series with eachother and with the winding of said relay,- whereby one ammeter indicatesthe magnitude of maxima effects and the second ammeter indicates themagnitude of minima effects of returned wave energy upon the currentflow in the oscillator circuit which includes said relay.

.a5 f 4. In an altimeter or the like, the combina tion with a vacuumtube oscillator and a relay for ues. and means preventing theinadvertent ener-l gizing of a subsequent signal device when the currentreaches for a second time the value which effected the energizing of aprevious signal device.

5. The invention asset forth in claim 4, in combination with manuallyoperated means for de-energizing the energized signal devices to resetthe apparatus.

6. In a device of the type stated, the combination with a relayincluding a contact arm movable between a pair of contacts, of a seriesof signal devices and switch means actuated by the alternate engagementof said contact arm with the respective contacts for progressivelyenergizing said signal devices when the current flow y through saidrelay alternately varies in opposite sense by progressively increasingincrements.

7. The invention as set forth in claim 6, wherein said signal devicescomprise lamps, in combination with means in series therewith to limitthe initial current flow prior to the heating of the lamp filaments.

8. In a device of the type stated, the combination with an oscillator,a-relay having the winding thereof included in a circuit which forms apath for the space current of said oscillator, said relay having acontact arm movable between and adapted to engage the respectivecontacts of a pair of contacts when the current through said windingrises to a predetermined maximum orr falls below a predeterminedminimum, of a series d signal devices, and switch means forprogressiveiy energizing said signal devices as the cur-` rent ilow insaid circuit varies from a mean value `,combination with meansestablishing a resistive shunt around said relay winding when saidswitch means is actuated to energize a given signal device, whereby thesensitivity of the relay lis reduced.

10. In distance measuring apparatus of the reected wave energy type, thecombination with an oscillator and a relay responsive to changes incurrent now due to the reaction upon said oscillator of wave energyreilected back to the same,

o! a plurality of signal devicesswitch means for completing circuits toenergize said signal devices progressively, and means controlled by saidrelay for eiiecting the actuation of said switch means.

11. 'Ihe invention as set iortligv in claim 10, wherein said switchmeans comprises a rotatable cylinder having a. conducting segment at.the cylindrical surface thereof, and Vfixed contacts for engaging saidsegment at predetermined angular adjustments of said cylinder; and saidrelay@ controlled means comprises a spring tending to rotate saidcylinder, an-` escapement normally locking said cylinder againstrotation, and electro-magnetic means for actuating said escapement uponthe closure of the relay circuit.

12. A device for determining the `distance between an aeroplane and areflecting surface comprising, a distance measuring device located onsaid plane including a thermionic tube with input and output electrodescoupled in alternating current circuits to produce sustainedoscillations, means for coupling an antennasystem to said circuits toradiate energy towards said reflecting surface and to receive energyfrom said reilecting surface, direct current energizing circuitsconnected between the electrodes of said tubes, a relay including awinding in series withY one of said direct current energizing circuits,said relay having a movable armature, a plurality of indicating devices,a plurality of contacts located adjacent said movable armature, andcircuits cooperating with said contacts and with said indicating devicesvfor energizing said indicating de-4 vices when said armature isactuated by energizing current ilowing.\through said energizing 1g)circuits including said relay winding to close said 13. A device fordetermining the distancebetween an aeroplane and a reiiecting surfacecomprising, a distance measuring device located on 15 said planeincluding a thermionic tube with input -and output electrodes coupled inalternating current circuits to produce sustained oscillations, meansfor coupling an antenna system to said circuits to radiate energytowards said reflecting 20 surface and to receive energy from saidreflecting n surface, direct current energizing circuits conn nectedbetween the electrodes of said tubes. a relay including a winding inseries with one of said direct current energizing circuits', said relay2g having a movable armature, a series of indicating devices. energizingcircuits for each of said indicating devices, said circuits eachincluding =a switch comprising conducting elements located on a movableelement and ilxed contacts in the 30 path of movement of said member,and means for progressively closing said switches and energizing saidindicating devices as the current intensity in said relay winding risesand falls due to the eifect of reflected energy on the oscillationsproduced in 3,-,

said oscillator including, a plurality of contacts located adjacent thearmature of said relay, and

a second relay adapted when energized to move said contact carryingmovable member, said last named relay being energized by circuits closed40 by movement of said armature in response to current flowing in saidwinding of said rst named relay.

FREDERICK fr. BRAKE.

